Endocrine Abstracts

Background: Insulin autoimmune syndrome (IAS) or Hirata disease, is a rare cause of hyperinsulinemic hypoglycemia characterized by autoantibodies to endogenous insulin in individuals without previous exposure to exogenous insulin. IAS has been described as a form of type VII hypersensitivity, characterized by the presence of autoantibodies against a circulating antigen. The cornerstone of the IAS is the appearance of circulating insulin autoantibodies (IAA), which have a pathogenic role in the development of the syndrome. Occasionally It develops when a triggering factor that is a medication or a viral infection acts on an underlying predisposing genetic background. Here, we report a case of Insulin Autoimmune Syndrome.

Clinical presentation: 43 years old Asian woman presenting to the ER with diaphoresis and tremors for the past 10 days duration. She had 3-4 episodes/day and were triggered by fasting and exercise. Her blood glucose when checked was noted to be 45 mg/dl. Patient was administered dextrose infusion and evaluated for hypogylcemia. She is non diabetic, no other comorbidities and was not on any medications. General physical examination revealed an obese, alert and healthy female. Her blood pressure 130/82 mmHg and pulse rate was 84/min. She was admitted for 72 hour fast test, patient was kept NPO and closely monioted for symptomatic hypoglycemia. Patient developed diaphoresis and tremors, blood glucose of 50 mg/dl, Samples for insulin, C- peptide, Pro Insulin, serum Beta hydroxy butyrate, and urine ketones were collected, fast terminated and patient was given oral carbohydrates and her condition improved confirming presence of Whipples triad. Her laboratory investigations revealed renal function, liver function tests, thyroid profile and hemogram to be normal. Her 8 am cortisol 12, Hba1c:5.5, Insulin >1000.0 mIU/ml, Pro insulin 69.70 pmol/l (<11), Beta butyric acid <60 umol/l.C-peptide 6.29 ng/ml (0.78-5.19), Insulin antibody >100 U/ml (>10 positive). Usg Abdomen was normal. Contrast enhanced CT abdomen was performed to look for pancreatic pathology and was normal. Diagnosis of Insulin autoimmune syndrome is made. She was adviced frequent small meals and also treated with steroids for a week. On follow up she had resolution of her symtpoms.

Conclusion: The diagnosis of IAS is challenging and should be considered in any patient undergoing evaluation for hypoglycemia. Discrepancies between an unusually high insulin concentration and slightly raised proinsulin and C-peptide levels, with a concurrent insulin to C-peptide molar ratio of > 1, are suggestive of IAS.